Comparative analysis of the static and dynamic dehumidification performance of metal-organic framework materials

Figures & data

Fig. 1. Schematic illustration of the experimental setup for performance evaluation of the desiccant-coated heat exchanger under dynamic testing conditions.

Table 1. Major equipment lists for the experimental setup.

Item	Type	Specifications	Model, Company	Instrument uncertainty^a
Environmental chamber 1	Programmable constant temperature and humidity	100–200 °C ± 0.05 °C, 0–100% RH ± 0.1% RH)	Model MHD-1, Terchy Environmental Technology, Taiwan	0.02 °C 0.05% RH
Environmental chamber 2	Programmable constant temperature and humidity	0-100 °C ± 0.3 °C, 10-98% RH ± 3% RH,	Model-150-00-SP-SD, Giant Force Instrument Enterprise Co., Ltd., Taiwan	0.17 °C 0.05% RH
Water tank	Constant temperature	20 °C–100 °C ± 0.1 °C	D-620, Wejida Enterprise, Taiwan	0.05 °C
Humidity and temperature probe	Resistance type	0-100% RH ± 0.8% RH, 40-85 °C ± 0.1 °C	HF532, Rotronic Inc., Bassersdorf, Switzerland	0.46% RH 0.05 °C
Data logger	Paperless recorders	0-100 % RH ± 0.1% RH, 270-2000 °C ± 0.1 °C	GL840 M, GRAPHTEC Inc., Tokyo, Japan	0.05% RH 0.05 °C
Weighing scale	Precision scale	0–320 g ± 0.003 g	Model-AB323, Dehe Weighing Apparatus Co., Ltd., Taiwan,	0.001 g
Hot plate	electric	0–350 °C ± 1 °C	Electric heating plate (Model-HP303D, Ten Billion Technology Co., Ltd.)	0.5 °C

^a Uniform probability distribution function (pdf) is used to calculate standard uncertainty of instrumentation.

Fig. 2. BET analysis of MOF (A520) and Sorbead R to quantify the surface area and porosity of the desiccant materials.

Fig. 3. Adsorption ability curves under environmental temperatures of 25 °C and 30 °C and relative humidity varying from 60% RH to 80% RH for (A) Sorbead R and (B) MOF-A520.

Table 2. Static adsorption ability of Sorbead R and MOF-A520 after 2 hours of adsorption under different environmental conditions.

Adsorption ability of Sorbead R and MOF-A520: (${AA}_{d, s}:$ unit g/g)
Environmental conditions Desiccants	60% RH		70% RH		80% RH
	25 °C	30 °C	25 °C	30 °C	25 °C	30 °C
Sorbead R	0.247	0.260	0.306	0.320	0.341	0.340
MOF-A520	0.313	0.309	0.344	0.338	0.392	0.390

Fig. 4. Adsorption capacities under environmental temperatures of 25 °C and 30 °C and relative humidity varying from 60% RH to 80% RH for (A) Sorbead R and (B) MOF-A520.

Table 3. Maximum static adsorption capacities (${MC}_{\mathit{vap},s}$) of the two desiccants under different environmental conditions.

Maximum adsorption capacity ($\times {10}^{-4}$ g/(g*s))
Environmental conditions Desiccants	60% RH		70% RH		80% RH
	25 °C	30 °C	25 °C	30 °C	25 °C	30 °C
Sorbead R	1.31	1.36	1.72	1.82	2.13	2.01
MOF-A520	1.86	1.92	2.29	2.31	2.61	2.83

Fig. 5. Total residual mass inside desiccants during the desorption process at an environmental temperature of 30 °C and a relative humidity of 70% RH for (A) Sorbead R and (B) MOF-A520 at different regeneration temperature (RT) settings.

Table 4. Final residual amount per unit mass of MOF-A520 and Sorbead R with different regeneration temperatures under different environmental conditions.

Final residual amount per unit mass of MOF-A520 and Sorbead R (RESM, g/g)
Regeneration temp. Environmental conditions	40 °C		50 °C		60 °C		70 °C		80 °C
	MOF-A520	Sorbead R	MOF-A520	Sorbead R	MOF-A520	Sorbead R	MOF-A520	Sorbead R	MOF-A520	Sorbead R
25 °C/60%RH	0.261	0.135	0.033	0.069	0.017	0.043	0.012	0.027	0.008	0.015
25 °C/70%RH	0.286	0.192	0.060	0.082	0.019	0.050	0.012	0.030	0.008	0.014
25 °C/80%RH	0.294	0.253	0.149	0.097	0.014	0.057	0.013	0.032	0.009	0.016
30 °C/60%RH	0.292	0.196	0.165	0.087	0.026	0.056	0.013	0.031	0.008	0.018
30 °C/70%RH	0.302	0.272	0.246	0.137	0.025	0.061	0.013	0.037	0.008	0.022
30 °C/80%RH	0.320	0.286	0.274	0.173	0.036	0.068	0.023	0.041	0.011	0.021

Table 5. Water removal percentage of MOF-A520 and Sorbead R with different regeneration temperatures under different environmental conditions.

Water removal percentage (WRP) of MOF A520 and Sorbead R in the desorption process (%)
Regeneration temp. Environmental conditions	40 °C		50 °C		60 °C		70 °C		80 °C
	MOF-A520	Sorbead R	MOF-A520	Sorbead R	MOF-A520	Sorbead R	MOF-A520	Sorbead R	MOF-A520	Sorbead R
25 °C/60%RH	16.3%	45.6%	89.3%	71.7%	94.6%	83.5%	96.3%	89.1%	97.5%	93.7%
25 °C/70%RH	16.8%	36.2%	81.9%	73.7%	94.4%	83.3%	96.5%	89.9%	97.5%	95.3%
25 °C/80%RH	29%	22.7%	63.5%	70.2%	96.7%	82.3%	96.7%	90.3%	97.8%	95%
30 °C/60%RH	7.8%	30.3%	47%	69.3%	91.7%	80.1%	95.7%	88.9%	97.3%	93.6%
30 °C/70%RH	13%	13.7%	28.8%	57.7%	92.9%	80.6%	96.2%	88.2%	97.6%	93.1%
30 °C/80%RH	30.1%	10.5%	39.7%	44.5%	92.1%	79%	94.9%	87.4%	97.5%	93%

Fig. 6. Water removal capacity under an environmental temperature of 30 °C and a relative humidity of 70% RH for (A) Sorbead R and (B) MOF-A520.

Table 6. Maximum desorption capacity per unit gram of MOF-A520 and Sorbead R under different environmental conditions and regeneration temperatures.

Maximum desorption capacity per unit gram of desiccant ($\times {10}^{-4}$ g/(g*s))
Regeneration temp. Environmental conditions	40 °C		50 °C		60 °C		70 °C		80 °C
	MOF-A520	Sorbead R	MOF-A520	Sorbead R	MOF-A520	Sorbead R	MOF-A520	Sorbead R	MOF-A520	Sorbead R
25 °C/60%RH	1.12	0.53	2.08	0.85	4.01	1.25	5.73	1.91	8.03	2.27
25 °C/70%RH	1.26	0.58	2.22	1.02	4.13	1.60	6.20	2.01	8.36	2.54
25 °C/80%RH	2.05	0.64	3.65	1.12	5.56	1.64	7.61	2.59	9.11	3.41
30 °C/60%RH	0.68	0.55	1.53	1.00	3.20	1.83	5.52	2.44	7.85	3.65
30 °C/70%RH	1.02	0.55	2.26	1.01	3.74	1.86	5.71	2.46	8.13	3.72
30 °C/80%RH	1.54	0.56	3.46	1.04	5.44	1.88	7.73	2.50	9.89	3.74

Fig. 7. Humidity ratio of the process air behind the DCHE in dynamic operation under the process air supply temperature and the relative humidity of 30 °C and 80%RH with different regeneration temperatures. The inset picture highlights the dehumidification curve for each tested regeneration temperature.

Table 7. Corresponding characteristics of the DCHE with MOF-A520 in dynamic operations under different process air humidity conditions and regeneration temperatures with a process air temperature of 25 °C and 30 °C. G_vap, G_A, and G_D denote the total vapor absorption vapor amounts, ratio of absorption vapor amounts per unit contact area of fins and vapor absorption amounts per unit mass of MOF-A520. The DEH and REG processes denote the dehumidification and regeneration processes, respectively.

Environmental conditions RT		25 °C/60% RH		25 °C/70% RH		25 °C/80% RH		30 °C/60% RH		30 °C/70% RH		30 °C/80% RH
		DEH process	REG process	DEH process	REG process	DEH process	REG process	DEH process	REG process	DEH process	REG process	DEH process	REG process
$G_{\mathit{vap}}$ (unit: g)	50 °C	87.48	72.20	92.61	75.61	96.83	79.93	89.50	88.30	108.28	87.85	179.45	161.00
	60 °C	95.07	85.65	107.14	96.90	117.79	113.59	109.87	113.98	138.74	145.24	209.68	213.41
	70 °C	89.85	100.45	97.31	108.75	109.99	97.00	112.45	112.90	146.98	162.07	223.89	239.96
	80 °C	86.94	107.46	97.95	118.25	108.84	123.50	110.47	103.63	133.27	150.13	207.19	223.64
$G_a$ (unit: g/cm^2)	50 °C	0.018	0.015	0.019	0.016	0.020	0.017	0.019	0.018	0.022	0.018	0.037	0.033
	60 °C	0.020	0.018	0.022	0.020	0.024	0.024	0.023	0.024	0.029	0.030	0.043	0.051
	70 °C	0.020	0.022	0.020	0.023	0.024	0.021	0.023	0.023	0.030	0.034	0.049	0.053
	80 °C	0.019	0.023	0.020	0.024	0.024	0.027	0.023	0.021	0.028	0.031	0.043	0.046
$G_{\mathrm{m}}$ (unit: g/g)	50 °C	0.246	0.203	0.261	0.213	0.273	0.225	0.252	0.249	0.305	0.247	0.505	0.454
	60 °C	0.268	0.241	0.302	0.273	0.332	0.320	0.310	0.321	0.391	0.409	0.590	0.601
	70 °C	0.253	0.283	0.274	0.306	0.310	0.273	0.317	0.319	0.414	0.457	0.631	0.676
	80 °C	0.245	0.303	0.276	0.333	0.307	0.348	0.311	0.292	0.375	0.423	0.584	0.630

Table 8. The corresponding specific moisture extraction ratio (SMER) values and thermal coefficient of performance (COP_th) of the DCHE with MOF-A520 in dynamic operation under different process air environmental conditions and regeneration temperatures.

SMER and COPth of DCHE with MOF-A520
Regeneration temp. Environmental conditions	50 °C		60 °C		70 °C		80 °C
	SMER	COPth	SMER	COPth	SMER	COPth	SMER	COPth
25 °C/60 %RH	0.149	0.142	0.126	0.156	0.098	0.162	0.081	0.185
25 °C/70 %RH	0.159	0.136	0.138	0.141	0.106	0.150	0.091	0.157
25 °C/80 %RH	0.175	0.127	0.153	0.132	0.114	0.141	0.101	0.151
30 °C/60 %RH	0.158	0.290	0.141	0.213	0.118	0.194	0.105	0.179
30 °C/70 %RH	0.187	0.329	0.172	0.252	0.150	0.203	0.123	0.179
30 °C/80 %RH	0.278	0.437	0.247	0.339	0.215	0.260	0.177	0.215

Fig. 8. Average cooling capacity in the dehumidification process, the required average regeneration power in the regeneration process and the total power consumption in dehumidification and regeneration processes with different regeneration temperatures under the (A) process air temperature of 25 °C and relative humidity of 80%. (B) Process air temperature of 30 °C and relative humidity 80%.